A router is a type of power tool which is commonly used to make cuts of predetermined depth into the surface of a workpiece, or to finish the ends or edges of workpieces to be joined at a seam or joint. A router generally consists of a cutting bit driven by a motor supported in a housing attached to a base plate, which rests on the workpiece. The router is usually adjustable to make a cut of the desired depth and can be manipulated as necessary to form a cut of the desired shape in the workpiece.
Various attachments for guiding routers have been available heretofore. For example, U.S. Pat. Nos. 4,143,691 and 3,716,085 relate to attachments to facilitate cutting arcs in workpieces. U.S. Pat. Nos. 4,323,100 and 3,635,268 show guides for making circular cuts of different radii. U.S. Pat. No. 4,252,164 shows an attachment for cutting an end of circular cross section onto a rectangular workpiece. U.S. Pat. No. 4,102,370 shows an attachment for continuous depth of cut adjustment. U.S. Pat. No. 3,913,447 illustrates a guide for mitering the end of a workpiece. U.S. Pat. No. 3,376,787 shows an attachment for guiding a router along an irregular or curved workpiece edge. U.S. Pat. No. 3,332,462 shows an attachment for template routing.
Of the various router attachments and guides available, however, I am aware of only one router attachment which is particularly adapted for forming precise joints and seams with inlay material. These attachments are available from Art Betterley Enterprises, Inc., of Blaine, Minn. They include an adjustable bottom plate which defines with the base plate of the router a slot for receiving the edge of a sheet of laminate to be cut. The base plate includes a fixed follower comprising a lateral straight locating edge or lip which follows along the edge of the adjoining piece to cut the laminate to fit. The Betterley attachment, however, is adapted for use with straight seams and is neither adapted nor intended for cutting arcuate joints of inside or outside curvature.
There is thus a need for an improved router attachment which can be used with either straight seams or arcuate seams, of inside or outside curvature, to form precise seams and joints of the type required in patching and inlay work.